The present invention relates to a method and apparatus for simultaneously mechanically treating the surface of small parts and in particular to a drum tumbling apparatus for grinding and/or polishing particulate materials such as small machine parts, nuts, bolts and the like.
Drum apparatus for the grinding and/or polishing of metallic parts and the like are already known. In general such apparatus comprises a cylindrical drum, rotatable about its central axis having an opening at one end for the supply of material to be treated and the polishing media (generally an aqueous mixture of abrasives) and an opening at its other end for the discharge of the material and the media. In this type of installation, the ability of feeding the material and media from one end while simultaneously discharging it from the other end, permits the processing of small parts in a continuous operation. The material throughput can be adjusted by regulating the supply at the inlet end while simultaneously regulating the rotation of the drum. The material fed at the inlet acts to push the material already in the drum outwardly of the discharge opening, this movement being enhanced by the speed of rotation of the drum. Because of the automatic passage of the material through the drum, the length of time that the material spent in the drum was generally insufficient to obtain optimum surface treatment and it was therefore necessary, in the past, to superimpose upon the drum a second rotary movement about an axis other than the central axis of the drum, so as to create centrifugal forces which would accelerate the scouring or polishing process. As a result of the added centrifugal force, the material was capable of being completely treated even during only a short passage through the drum. For this purpose, at least two drums were mounted so as to be rotatable with their ends diametrically opposite one another between two supporting discs. The supporting discs were also driven so that in the course of operation the drums would be rotated about their own axes and perform a revolving motion about the axis of the discs. Such apparatus was shown and described in the German Pat. publication No. 2135,052 and in United States It will be obvious, however, that the known apparatus was complex in both its structure and in its operation.
It is the object of the present invention to provide drum grinding and polishing apparatus which is simple in structure and easily employed.
It is a further object of the present invention to provide drum grinding and polishing apparatus in which the operations can be carried out both in the batch and/or in the continuous processes.
It is a further object of the present invention to provide drum grinding and polishing apparatus in which the drum is caused to rotate only about its own central axis and yet provide the necessary control and regulation of the rate of throughput.
It is a general object of the present invention to provide drum grinding and polishing apparatus which is improved over the prior art and which overcomes the disadvantages and defects of the known apparatus.
The foregoing objects, other objects and numerous advantages of the present invention will be apparent from the following disclosure thereof.